The present invention relates in general to composite fabrics and in particular to composite fabrics with features that allow user adjustment of the fabric thermal insulation properties.
Man has been using clothing for a considerable time to help in the adaptation to the world""s variable and sometimes harsh environment. Because of the many variations in the world""s environment, the fabric that makes up clothing is required to do many duties. Sometimes the environment requires insulation to protect against cold temperatures. Many times these cold temperatures are accompanied with wind and rain. Therefore the fabrics that makes up the clothing may need to be able to keep water out while also keeping heat next to the clothing wearer where it is needed. If the cold weather occurs during sunny conditions, then the user may be faced with having to change clothing as the temperature varies. Usually this is done by applying clothing in layers. When the clothing is in layers, then the user may remove selected layers of clothing as the temperature warms up. While wearing clothing in layers is effective, many times it is cumbersome to remove and store the clothing layers.
Some companies (e.g., Gore Tex Corp.) have developed materials with a fabric pore size such that water molecules cannot penetrate yet water vapor can escape. While this solves the problem of keeping moisture out and at the same time allowing the fabric to breathe, it does not solve the problem of how to deal with a requirement for a variable thermal insulation for clothing. For example, if one dresses for a cold morning and the sun comes out, then the additional thermal energy may require a person to remove clothing layers or to make some adjustment for the added heat load.
A dead air space is known to be a very good thermal insulator. This concept is used effectively in air mattresses and other inflatable materials to provide insulation or cushioning. While some manufacturers have tried to use air in materials for garment clothing, it has resulted in bulky garments with a very course control of insulation. Most of these manufacturers use the thickness of the air space to control the amount of insulation. Since creating pockets of air requires that the pockets be impervious to the air molecule, this precludes the use of materials that naturally breathe. It is difficult to design a composite fabric that allows the use of air as an insulator, allows easy inflation and deflation, and allows the use of materials that naturally breathe.
Sometimes it is desirable for clothing required for variable weather conditions to have the ability to vary its thermal insulation at selected areas rather than over the entire garment. In this way, only those portions of a user""s body that need additional insulation would be affected. For example, one may have their back against damp ground while their front is exposed to direct sunlight. It would be desirable to be able to change the thermal insulation of the garment covering one""s back to have one thermal insulation value while adjusting the thermal insulation of the garment covering the front to have a different thermal insulation value.
There is, therefore, a need for a composite fabric that enables adjustments of thermal insulation in selected areas while maintaining the ability to use fabrics that naturally breathe in other selected areas.
A composite fabric is formed by attaching one or more expandable bladders to a surface of a first fabric layer at spaced intervals across the surface and extending corresponding bladder lengths across the surface in a direction substantially transverse to a direction of the spaced intervals. The expandable bladders define fabric areas of the first fabric layer adjacent to each of the corresponding bladder lengths of the expandable bladders. In one embodiment, each expandable bladder is attached to the first fabric layer by one or more fabric loops. The expandable bladders are threaded through corresponding fabric loops that extend across the surface of the fabric layer. The expandable bladders are coupled, singly or in groups, via an air valve that connects to an air source for selectively inflating and deflating the expandable bladders. When selected, expandable bladders are inflated and deflated and the fabric areas along and adjacent to the selected expandable bladders are selectively covered and uncovered by the selected expandable bladders. In this manner, the thermal insulation of the defined fabric areas of the fabric layer are varied.
In one embodiment, the fabric loops extend continuously across the fabric layer. Each fabric loop is made from a non-stretch fabric and essentially hangs in folds when the expandable bladders in the fabric loops are deflated. The fabric loops may be porous and offer little insulation value so that the characteristics of the first fabric layer are preserved when not covered by expandable bladders. The expandable bladders may be made to have a certain compressed shape when the air inside is evacuated. In another version of this embodiment, the fabric loops are segmented across the length of the fabric layer and do not cover the entire bladder lengths of corresponding threaded expandable bladders.
In another embodiment of the present invention, the fabric loops are made from a material that, while porous, stretches in a radial direction with little or no length expansion. The expandable bladders are threaded through corresponding fabric loops and assume a compressed shape smaller than the diameter of a non-expanded fabric loop. When air is supplied to selected expandable bladders, they unfold, expand, and stretch their corresponding fabric loops thereby selectively covering the fabric area adjacent to and along the bladder lengths of the selected expandable bladders. In this manner, the thermal insulation of the fabric area of the selected expandable bladders is varied. In this embodiment, the fabric loops may also be segmented across the length of the fabric layer.
In one embodiment, the expandable bladders are made as tubes of thin material that may be folded to a minimum cross-section within a fabric loop. When the expandable bladders are pressurized with air, they unfold and either fill or expand a corresponding fabric loop. In another embodiment, the expandable bladders have a cross-section geometry designed so that they assume a certain collapsed shape when evacuated. These extendable bladders unfold in a controlled geometry when filling or expanding a corresponding fabric loop. In yet another embodiment, the expandable bladder is made from a balloon-like structure that expands rapidly to a fixed diameter when inflated. The tapered wall thickness of a balloon-like expandable bladder causes its expansion to progress along its bladder length as it is pressurized. This balloon-like expandable bladder varies the thermal insulation of the fabric layer by selectively covering and uncovering the fabric area as its inflation and deflation progresses across its bladder length.
The composite fabric may be used to make fabric products with various functional shapes. For example, a fabric garment may be made by piecing together sections of composite fabric made according to embodiments of the present invention. A user may selectively inflate expandable bladders to modify and control the thermal insulation across selected areas of the fabric garment. Various fabric products may be formed by using the composite fabric made according to embodiments of the present invention including, but not limited to, tents, sleeping bags, backpacks, shoes, boots, and garments worn by an individual.
The expandable bladders may be coupled to an air source with various air valves so that a user may also selectively inflate and deflate expandable bladders. The expandable bladders may also be connected in series so that an entire area of the fabric layer may be controlled with one air valve. The couplings that connect expandable bladders in series may be designed to be flexible to facilitate bending a composite fabric layer.
The foregoing has outlined rather broadly the features and technical advantages of the present invention in order that the detailed description of the invention that follows may be better understood. Additional features and advantages of the invention will be described hereinafter which form the subject of the claims of the invention.